Assess solar UV intensity with VEML6075 and PIC18F2458 to improve energy conversion efficiency

The future of UV light measurement

Published Nov 01, 2023

Click board™

UV2 Click

Dev Board

EasyPIC v7a

Compiler

NECTO Studio

MCU

PIC18F2458

Dive into the fascinating realm of UV light measurement with our innovative solution, and unlock the potential to safeguard health, optimize processes, and advance scientific discovery

Hardware Overview

How does it work?

UV2 Click is based on the VEML6075, a UVA and UVB light sensor with an I2C interface from Vishay. The UVA and UVB have their own individual channels, along with the UVD as a dummy channel for dark current cancellation and UVcomp1 and UVcomp2, parts of a normalized spectral response. All those values are essential for deriving the UV radiation values from the sensor readings. The measurement results are stored in separate registers. They remain in registers and can be read from them until the device wakes up and a new measurement is made. The UVB rays

wavelengths ranging from 280nm to 320nm are extremely energetic and harmful for the skin to the extent that they are responsible for 65% of skin tumors. Thankfully, only 0.1% of the solar energy that arrives on the earth’s surface is in the shape of UVB radiation. The UVA ray wavelengths ranging from 320nm to 400nm are less powerful than the previous ones but highly penetrating. They can reach the skin, becoming responsible for photoaging and promoting the onset of different forms of skin cancer. 4.9% of solar energy is made up of UVA rays. The UV2 Click communicates

with the host MCU using an I2C interface over the mikroBUS™ socket, supporting Standard (100KHz) and Fast (400KHz) operating frequencies. This Click board™ can be operated only with a 3.3V logic voltage level. The board must perform appropriate logic voltage level conversion before using MCUs with different logic levels. Also, it comes equipped with a library containing functions and an example code that can be used as a reference for further development.

Features overview

Development board

EasyPIC v7a is the seventh generation of PIC development boards specially designed for the needs of rapid development of embedded applications. It supports a wide range of 8-bit PIC microcontrollers from Microchip and has a broad set of unique functions, such as the first-ever embedded debugger/programmer over USB-C. The development board is well organized and designed so that the end-user has all the necessary elements in one place, such as switches, buttons, indicators, connectors, and others. With four different connectors for each port, EasyPIC v7a allows you to connect accessory boards, sensors, and custom electronics more efficiently than ever. Each part of the EasyPIC v7a development board

contains the components necessary for the most efficient operation of the same board. In addition to the advanced integrated CODEGRIP programmer/debugger module, which offers many valuable programming/debugging options and seamless integration with the Mikroe software environment, the board also includes a clean and regulated power supply module for the development board. It can use various external power sources, including an external 12V power supply, 7-23V AC or 9-32V DC via DC connector/screw terminals, and a power source via the USB Type-C (USB-C) connector. Communication options such as USB-UART and RS-232 are also included, alongside the well-

established mikroBUS™ standard, three display options (7-segment, graphical, and character-based LCD), and several different DIP sockets. These sockets cover a wide range of 8-bit PIC MCUs, from PIC10F, PIC12F, PIC16F, PIC16Enh, PIC18F, PIC18FJ, and PIC18FK families. EasyPIC v7a is an integral part of the Mikroe ecosystem for rapid development. Natively supported by Mikroe software tools, it covers many aspects of prototyping and development thanks to a considerable number of different Click boards™ (over a thousand boards), the number of which is growing every day.

Microcontroller Overview

MCU Card / MCU

Architecture

PIC

MCU Memory (KB)

Silicon Vendor

Microchip

Pin count

RAM (Bytes)

2048

Used MCU Pins

mikroBUS™ mapper

RST

SCK

MISO

MOSI

Power Supply

3.3V

Ground

GND

PWM

INT

I2C Clock

RC3

SCL

I2C Data

RC4

SDA

Ground

GND

Take a closer look

Schematic

Step by step

Project assembly

EasyPIC v7a front image hardware assembly

Start by selecting your development board and Click board™. Begin with the EasyPIC v7a as your development board.

NECTO Output Selection Step Image hardware assembly

In the advanced settings, pay special attention to the Redirect standard output field. By default, it is set to Application output as the method of displaying final results. To show results via a UART terminal, select the “UART” option in that field and click the “SAVE” button. You will be returned to the Compiler field, and now you can move on to the next step by pressing the “NEXT” button.

Rotary B 2 Click front image hardware assembly

EasyPIC v7a MB 2 - upright/background hardware assembly

NECTO Compiler Selection Step Image hardware assembly

Necto DIP image step 7 hardware assembly

EasyPIC PRO v7a Display Selection Necto Step hardware assembly

Track your results in real time

Application Output

After pressing the "FLASH" button on the left-side panel, it is necessary to open the UART terminal to display the achieved results. By clicking on the Tools icon in the right-hand panel, multiple different functions are displayed, among which is the UART Terminal. Click on the offered "UART Terminal" icon.

Once the UART terminal is opened, the window takes on a new form. At the top of the tab are two buttons, one for adjusting the parameters of the UART terminal and the other for connecting the UART terminal. The tab's lower part is reserved for displaying the achieved results. Before connecting, the terminal has a Disconnected status, indicating that the terminal is not yet active. Before connecting, it is necessary to check the set parameters of the UART terminal. Click on the "OPTIONS" button.

In the newly opened UART Terminal Options field, we check if the terminal settings are correct, such as the set port and the Baud rate of UART communication. If the data is not displayed properly, it is possible that the Baud rate value is not set correctly and needs to be adjusted to 115200. If all the parameters are set correctly, click on "CONFIGURE".

The next step is to click on the "CONNECT" button, after which the terminal status changes from Disconnected to Connected in green, and the data is displayed in the Received data field.

Software Support

Library Description

This library contains API for UV2 Click driver.

Key functions:

uv2_set_active_force_mode - This function set active force mode by write force mode UV_AF bit to config register of VEML6075 sesnor on UV 2 Click
uv2_get_uva - This function get UVA data by read UVA register value of VEML6075 sesnor on UV 2 Click
uv2_get_uvb - This function get UVB data by read UVB register value of VEML6075 sesnor on UV 2 Click.

Open Source

Code example

This example can be found in NECTO Studio. Feel free to download the code, or you can copy the code below.

/*!
 * \file 
 * \brief UV2 Click example
 * 
 * # Description
 * This app measurement UVA and UVB data and calculate UV index level.
 *
 * The demo application is composed of two sections :
 * 
 * ## Application Init 
 * Initialization device and set default cinfiguration.
 * 
 * ## Application Task  
 * This is a example which demonstrates the use of UV 2 Click board.
 * UV 2 Click communicates with VEML6075 sesnor via I2C by write to register and read from register.
 * This example measurement UVA and UVB data, calculate UV index level and write log.
 * Results are being sent to the Usart Terminal where you can track their changes.
 * All data logs write on usb uart changes for every 2 sec.
 * 
 * \author MikroE Team
 *
 */
// ------------------------------------------------------------------- INCLUDES

#include "board.h"
#include "log.h"
#include "uv2.h"

// ------------------------------------------------------------------ VARIABLES

static uv2_t uv2;
static log_t logger;

// ------------------------------------------------------ APPLICATION FUNCTIONS

void application_init ( void )
{
    log_cfg_t log_cfg;
    uv2_cfg_t cfg;

    uint8_t state_id;

    /** 
     * Logger initialization.
     * Default baud rate: 115200
     * Default log level: LOG_LEVEL_DEBUG
     * @note If USB_UART_RX and USB_UART_TX 
     * are defined as HAL_PIN_NC, you will 
     * need to define them manually for log to work. 
     * See @b LOG_MAP_USB_UART macro definition for detailed explanation.
     */
    LOG_MAP_USB_UART( log_cfg );
    log_init( &logger, &log_cfg );
    log_info( &logger, "---- Application Init ----" );

    //  Click initialization.

    uv2_cfg_setup( &cfg );
    UV2_MAP_MIKROBUS( cfg, MIKROBUS_1 );
    uv2_init( &uv2, &cfg );

    Delay_ms( 100 );

    log_printf( &logger, "------------------------\r\n" );
    log_printf( &logger, "       UV 2  Click      \r\n" );
    log_printf( &logger, "------------------------\r\n" );

    uv2_default_cfg( &uv2 );
    
    state_id = uv2_check_id( &uv2 );
    
    if ( state_id )
    {
        log_printf( &logger, "       Configured       \r\n" );
    }
    else
    {
        log_printf( &logger, "         ERROR          \r\n" );
    }

    log_printf( &logger, "------------------------\r\n" );
    Delay_ms( 100 );
}

void application_task ( void )
{
    uint16_t val_uva;
    uint16_t val_uvb;
    float uv_index;

    val_uva = uv2_get_uva( &uv2 );
    log_printf( &logger, " UVA data = %d \r\n", val_uva );

    val_uvb = uv2_get_uvb( &uv2 );
    log_printf( &logger, " UVB data = %d \r\n", val_uvb );

    uv_index = uv2_get_uv_index( &uv2 );
    log_printf( &logger, " UV Index = %f \r\n", uv_index );

    log_printf( &logger, "------------------------\r\n" );
    Delay_ms( 2000 );
}

void main ( void )
{
    application_init( );

    for ( ; ; )
    {
        application_task( );
    }
}

// ------------------------------------------------------------------------ END